Compare the syntax values to the ones in the specification

the first syntax variation is when the Array Constructor is called as a function (15.4.1):

[ item1 [ , item2 [ , … ] ] ]

the second variation is when the Array Constructor is called as part of a "new" expression (15.4.2). This variation takes 2 different kinds of parameters: items (15.4.2.1) and length (15.4.2.1), so show both: